In recent years, portable communication devices having a variety of housing structures are developed. Among others, a portable communication device has been developed wherein two housings are slidably moved in parallel with respect to each other in an overlapped state thereof. An example of the portable communication device having such a slidably-moving mechanism will be described with reference to FIG. 11 to FIG. 14. FIG. 11 to FIG. 14 are longitudinal-sectional views of a portable communication device having the slidably-moving mechanism.
The structure of the portable communication device will be described with reference to FIG. 11 and FIG. 12. FIG. 11 shows a closed state wherein a pair of housings have a maximum housing-overlapped area, whereas FIG. 12 shows an open state wherein the pair of housings in pair have a minimum housing-overlapped area. In the communication device, the front housing 110 disposed on the front side, i.e., shown at the top side in the drawing and the rear housing 120 disposed on the rear side, i.e., shown at the bottom side in the drawing are coupled together by a slide mechanism 130. The front housing 110 includes an LCD unit 111 on the front side of the housing, and a printed circuit board 112 and a first antenna 113 connected to the printed circuit board 112 within the housing. The rear housing 120 includes a keyboard 121 on the front side of the housing, and includes within the housing a battery 126, printed circuit boards 122, 125, a wireless circuit 124 mounted on the printed circuit board 122, and a second antenna 123 connected to the printed circuit board 122 and wireless circuit 124 within the housing. The printed circuit board 112 disposed in the front housing 110 and the printed circuit board 122 disposed in the rear housing 120 are connected together by a flexible printed cable (FPC) 131. The wireless circuit 124 installed in the rear housing 120 and the first antenna 113 installed in the front housing 110 are connected together by a coaxial cable 132.
In operation of the above device, the wireless circuit 124, upon communicating to an external device, typically inputs/outputs signals via the second antenna 123. If the user performs a keystroke etc. in the open state of the housings effected by the slide mechanism 130, a portion of the housing including the second antenna 123 is covered by the hand. In this state, there arises the problem that the communication characteristic of the second antenna 123 significantly deteriorates. In order to avoid such a problem, the portable communication device shown in FIGS. 11 and 12 uses the first antenna 113 provided in the front housing 110 if the user performs a keystroke etc. More specifically, the connection point of the wireless circuit 124 is switched from the second antenna 123 to the first antenna 113.
However, in the above structure, the coaxial cable 132 passing through the slide mechanism 130 is required to have a higher bending endurance in view of the stress applied thereto by a bend. A lower loss is also required between the first antenna 113 and the wireless circuit 124. Thus, it is needed for the coaxial cable 132 to have a sufficiently larger size for achieving the lower loss in the coaxial cable 132. However, if the coaxial cable 132 having a larger diameter passes through the slide mechanism 130, the slide mechanism 130 must have a larger thickness, thereby causing a difficulty in designing a smaller and thinner structure. In addition, the coaxial cable 132 having a larger diameter has a larger resistance with respect to the bending, and accordingly, a slide movement of the front housing 110 requires a larger effort to thereby cause a degraded operability of the slide mechanism.
In order to solve the above problem, a portable communication device shown in FIGS. 13 and 14 is known. FIG. 13 shows the closed state wherein the overlapped area of the pair of housings is the maximum, whereas FIG. 14 shows the open state wherein the overlapped area of the pair of housings is the minimum. In the portable communication device shown in those drawings, the front housing 210 disposed on the front side of the device and the rear housing 220 disposed on the rear side of the device are coupled by the slide mechanism 230. The front housing 210 includes an LCD unit 211 on the front side of the device and a printed circuit board 212 within the device. The rear housing 220 includes a keyboard 221 on the front side of the device, and includes within the device a battery 226, printed circuit boards 222, 225, a wireless circuit 224 mounted on the printed circuit board 222, a first antenna 213 and a second antenna 223 which are connected to the printed circuit board 222 and the wireless circuit 224. The printed circuit board 212 disposed in the front housing 210 and the printed circuit board 222 disposed in the rear housing 220 are connected together by an FPC231.
The portable communication device shown in FIGS. 13 and 14 employs a configuration wherein the first antenna 213 is disposed in the rear housing 220 at the position opposing the second antenna 223, and thus the coaxial cable does not pass through the slide mechanism 230, differently from the portable communication device shown in FIGS. 11 and 12. However, when the slide mechanism 230 is in an open state, the first antenna 213 installed in the rear housing 220 is covered by the slide mechanism 230 and the printed circuit board 212 installed in the front housing 210. In this case, there arises a problem in that the communication performance of the antenna is inferior as compared to the case where the antenna having the same volume is installed in the front housing 210. In addition, installation of the first antenna 213 in the rear housing 220 causes another problem in that the mounting area of the substrate 125 must be reduced in order for maintaining a volume equivalent to the volume of the rear housing 120 shown in FIGS. 11 and 12.
Patent Publication-1 discloses a technique for improving the communication characteristic of the antenna. In this patent publication, a pair of terminals that are in contact with each other in the open state of the housings is provided between the first housing and the second housing that slidably move with respect to each other. One of the terminals is connected to the printed circuit board within the first housing, whereas the other of the terminals is connected to the printed circuit board within the second housing. In this configuration, Patent Publication-1 uses the antenna installed within the first housing when the pair of housings are in the closed state. In the open state, the configuration is such that the terminals in pair connect together the printed circuit board in the first housing and the printed circuit board in the second housing, whereby the antenna installed in the second housing is used therein.
Patent Publication-1: JP-2006-303719A